The overall aim of the research program is to understand brain-behavior- hormone relationships underlying the reproductive cycle. One of the unanswered questions of behavioral endocrinology is how the brain integrates external environmental, internal hormonal and neural input. By identifying changes in neuropeptidergic expression associated with behavioral responses, we hope to characterize the ways in which the brain achieves this integration. Two specific experimental results, based on our own work with doves in the previous funding period, set the stage for the proposed research. The first involves VIP-like immunoreactivity in highly localized (ventrolateral periventricular) infundibular cells that increase in size during parental care. The second involves highly localized septal and (dorsolateral periventricular) infundibular CSF-contacting cells that co-express VIP and opsin-like immunoreactivity. VIP is a prolactin releasing factor, and prolactin is secreted at 2 distinct phases in reproduction - during the parental phase of the breeding cycle, and during the seasonal nonbreeding period. Experiments are designed to study the function of VIP, steroid-VIP interactions, species differences in the function of VIP cells, and the afferent and efferent projections of these cells. Another series of behavioral studies will be done to examine hormonal, thermal and stimulus factors regulating the sex-typical incubation behavior of the biparental ring doves. Here we ask about the doses and sites of action of steroids mediating sex-typical timing of incubation, the function of sex differences in timing of parental care, and the locus of the "biological clock" controlling daily rhythms of incubation.